A wind turbine blade usually comprises a load carrying structure. The load carrying structure is typically manufactured using fibre reinforcing material. The fibre reinforcing material is often stacked forming a plurality of stacked fibre layers. Today, the fibre layers are mostly selected from glass fibres or carbon fibres or hybrid material.
In carbon fibre blades, it is necessary to potential equalise the carbon fibres to the lightning protection system. Otherwise, static charges may build up or a lightning current from a lightning strike may inadvertently jump into the carbon fibres of the load carrying structure.
A copper mesh may be placed across sections or over the entire load carrying structure. The mesh connects the carbon content laminate with the lightning protection system earth/ground connections. However, high current tests have shown that local damages occur in areas in the interface between the mesh and the carbon laminate of the load carrying structure. These damages may cause delamination in the load carrying structure in areas and can thus lead to severe fatigue damage and failure of the blade.
WO 2007/062659 discloses a wind turbine blade with a lightning protection system with an inner lightning conductor and a lightning receptor arranged at the tip of the blade.
EP 1 112 448 discloses a wind turbine bladed with a carbon fibre reinforced load carrying structure, which is potential equalised to an inner down-conductor of a lightning protection system.
EP 1 664 528 also discloses a wind turbine blade and a carbon fibre reinforced load carrying structure. The wind turbine blade provided with a lightning protection system with an inner lightning conductor. The carbon fibres are potential equalised to the inner lightning conductor. A copper mesh can be used to provide a large contact surface to the carbon fibres.
There is the need for a solution to minimize or prevent such delamination and failures of the wind turbine blades.